1. Field of the Invention
This invention relates to an apparatus for use with musical instruments and, in particular, to an electrical apparatus for determining the pitch or fundamental frequency of a note emanating from a plucked or struck stringed musical instrument.
2. Description of the Prior Art
Prior art electrical devices for realizing a variety of sound effects in conjunction with musical instruments are known in the art. Operation of such devices in many cases is dependent upon first determining the pitch or fundamental frequency of a musical note being played. Apparatus for performing the latter function is also known in the art, but such apparatus has been either unreliable or expensive to construct.
One particular prior art apparatus for determining the pitch of a musical note is disclosed at pages 6b (3) and 6b (4) of the Musical Engineer's Handbook, published in 1975 by Electronotes. In the disclosed apparatus, an analog electrical signal representing the musical note, after amplification and filtering, is selectively fed, via a controlled analog switch, to a peak and downslope detector followed by a voltage controlled monostable multivibrator. The resultant output of the multivibrator is a train of electrical pulses whose period and, thus, fundamental frequency, are equal to those of the musical note.
For controlling the analog switch, the apparatus is further provided with a blanking circuit and a logic circuit. These two circuits act, in combination, to control the analog switch so that it feeds the entire analog signal to the peak and downslope detector for a set period of time after the inception of the signal. This, in turn, enables the multivibrator to establish an initial pulse train having an initial period and corresponding initial fundamental frequency. Thereafter, using the aforesaid pulse train, the blanking and logic circuits control the analog switch so that it now feeds to the detector only those portions of the analog signal which immediately surround the true maxima of the signal. In this manner, the apparatus, after establishing an initial fundamental frequency and period, is made substantially insensitive to any spurious peaks of the analog signal which might occur between the true maxima of such signal.
It is, therefore, a primary object of the present invention to provide an electrical apparatus for deriving the fundamental frequency of a musical note which gives improved performance and is less expensive to fabricate than prior art structures.
It is a further object of the present invention to provide an electrical apparatus of the aforesaid type which does not require the employment of analog switching techniques or analog switches.